1. Field of the Invention
This invention relates in general to a method and apparatus for reactive ion etching, and more particularly to a method and apparatus for achieving etch rate uniformity in a reactive ion etcher.
2. Description of Related Art
In the data storage industry, the most widely used storage device is the magnetic hard disk drive (HDD). The HDD uses magnetic heads, which fly over the magnetic disk, to read and write the data from/to the magnetic disk. In order for the head to fly over the disk in a predictable and stable fashion, the head is incorporated in a slider body with an air bearing surface (ABS) facing the disk. With a proper air bearing design, the slider can be flown very closely over the disk. Currently the flying height of the slider over the disk is in the range of 2-3 micro-inches (0.050-0.075 .mu.m), however the push to lowering the fly height is a never ending pursuit.
To achieve such a low fly height without crashing, it is critical that the fabricated ABS structure satisfies the designed requirements with tight tolerances. Several techniques have been used to produce such an ABS, including mechanical machining, ion milling, and reactive ion etching (RIE). For the more advanced ABS design such as Transverse Pressure Contour (TPC), there are steps on the ABS that are less than 1 micrometer deep. Consequently, the required tolerance is much tighter than mechanical machining can deliver. Ion milling has been the choice of the process for this type of step, however it does not have the throughput capacity like a reactive ion etcher. The technical challenge for reactive ion etching to produce such a step is the uniformity across the entire cathode.
The etch rate in a reactive ion etcher is higher around the cathode perimeter due to an edge effect on the plasma distribution and higher at the center because of the gas distribution, i.e., the gas inlet valve is typically at the center of the chamber. Many attempts have been conducted to modify the etch rate distribution, including modifying process parameters, such as gas pressure, gas composition, input power, etc. Other attempts to modify the etch rate distribution have focused on modifying chamber geometry, such as reactor can design, gas flow pattern, gas inlet shower head etc. While these methods have demonstrated that the rate uniformity can be improved, the overall distribution pattern remains unchanged.
It can be seen that there is a need for a method and apparatus for achieving etch rate uniformity in reactive ion etchers.
It can also be seen that there is a need for method and apparatus for tuning the overall distribution pattern in a reactive ion etcher to provide uniformity of the etch rate.